Axial flow compressors with adjustable stages



May 21, 1957 E. A. STALKER 2,792,983 AXIAL FLOW COMPRESSCRS wiTHADJUSTABLE STAGES Filed Nov. 5, 1954 2 Sheets-Sheet l INVENTOR.

y 1, 1957 E. A. STALKER 2,792,983

AXIAL FLOW COMPRESSORS WITH ADJUSTABLE STAGES Filed Nov. 5, 1954 2Sheets-Sheet 2 IN V EN TOR.

awn/aw t United States Patent l AXIAL FLOW COMPRESSORS WITH ADJUSTABLESTAGES Edward A. Stalker, Bay City, Mich. Application November 5, 1954,Serial No. 467,097 11 Claims. (Cl. 230-114) This invention relates tofluid machines having bladed rotors, such as compressors and the like.

An object of the invention is to provide increasing fluid mass flow withincreasing speed of rotation, particularly in the range of supersonicfluid speeds relative to the blades of the machines. 1

Other objects will appear from the description, drawings and claims.

When a bladed rotor, for instance an axial flow compressor rotor,achieves supersonic speed relative to the fluid, the mass flow ceases toincrease significantly with increasing time rate of rotation althoughthe pressure increases rapidly. This is a well known characteristic ofsupersonic flow. i

It is desirable to have the (time) rate of mass flow increase withincreasing rate of rotation of the rotor, or some variation in mass flowwith increasing pressure.

In this invention the rate of mass flow may be varied with respect tothe rate of rotation and/or with respect to the change in pressure.

Referring now to the drawings the above objects are accomplished by themeans illustrated in the accompanying drawings in which- Fig. 1 is afragmentary axial section through a compressor according to thisinvention;

Fig. 2 is a fragmentary development of the blading on line 2--2 in Fig.1;

Fig. 3 is a fragmentary section on line 3-3 in Fig. 1;

Fig. 4 is a fragmentary development on line 44 (same as 2-2) in Fig. lwith the front blades retracted;

Fig. 5 is a side view of the hub element of Fig. 1; and

Fig. 6 is a front axial view of the rotor of the com-. pressor of Fig.1.

Referring to the drawings the compressor is indicated generally as 10 inFig. 1. It comprises the case12 housing the rotor 14 mounted forrotation by its shaft 18 in bearing 20 which is supported by the statorhousing 22.

Fluid enters the case 12 through the annular inlet 24 and leaves thecompressor through the annular exit 26.

The rotor comprises the hub assembly 30 forming an annular duct 31 withthe case 12 and a plurality of axial flow blades 32 and 33 carried onthe hub assembly in two rows, the blades of each row being inperipherally spaced relation providing the rotor flow passages 34between them for the front row and passages 35 for the rear row. Theblade tips fit closely to the case to prevent significant back flow ofthe pumped fluid.

Fig. 2 shows the blades 32 positioned forward ofblades 33. Fig. 4 showsthe front blades retracted to positions between :the rear blades 33. Itwill be observed that the cross section of the duct 31 is larger at theleading edges of the rear blades than at the leading edges of the frontblades. Accordingly when the front blades are retracted to the rearblades the inlet cross sectional'areas of the passages between blades isincreased.

If the retraction of the front blades is made a function of therate ofrotation ofthe rotor the inlet cross-sec- 2 ,792,983 Patented May 21,1957 tional area can be made to increase with increasing rate ofrotation.

The surface 40 of the hub assembly is inclined radially inward along therearward or downstream direction of the general flow through thecompressor. That is the outside diameter of the hub assembly decreasesrearward along the rotor axis. Preferably the inside surface 46 of thecase is cylindrical so that one row of blades can be shifted axiallyrelative to the other while maintaining the same tip clearances with theinside surface of the case.

The retraction of the blades is accomplished by the mechanism shownparticularly in Figs. 1 and 3.

The rear blades 33 are carried on the hub rim 50. It has slots 52 (seeFigs. 2 and 4) which permit the front blades 32 to extend inward to themovable rim 58 which seals the slots 52 in the rim 50.

The rim 50 is integral or fixed to the disk 60 which is fixed to the hub62 suitably mounted on shaft 18 to rotate with it. t

The hub screw 62 carries the multiple threads 64 of pitch anglecorresponding to the helical path of each blade when it is movedaxially. The hub nut 68 engages the threads of the hub screw and isfixed to the disk 70 carrying the rim 58. When the nut is moved axiallyalong the screw the blades 32 move along their slots 52 with axial andperipheral components of motion.

The axial movement of the blades is made a function of a speed propertyof the rotor by means of the masses 72-75 shown in Figs. 1 and 3. As therotor increases in peripheral speed the masses move outward about theirhinges 78 carried in the brackets 80 fixed to disk 60. Each mass has thearm 82 connected to disk 70 by a link 84 to push the nut 68 rearward andwith it the front row of blades 32.

The forward axial movement of the blades occurs when the rotor slowsdown. The fluid forces on the blades act forward to move the bladesforward. These forces may be assisted also by a spring 87. See Fig. 1.

For a passage of fixed geometry and having a throat the time rate ofmass flow reaches a maximum for sonic velocity at the throat and doesnot increase significantly with increasing relative speed of the flow.

In the rotor of this invenion as the speed relative to the fluidincreases the inlet of each passage is increased in cross sectionalarea. The throat area is preferably also varied to have a suitablerelation to the inlet area. This is accomplished by the selection of theblade thickness and the contour of the surface 40 in axial planes.Preferably the cross sectional area at the throat decreases as the speedof rotation increases. See Figs. 2 and 4.

Preferably the blades have sharp leading edges with a small chordwiselength of concave surface extending rearward from the leading edge. Theyare also preferably thin and overlap in axial view throughout theirspans and the leading edge of a succeeding blade is preferably forwardchordwise of the mid-chord point of a preceding blade.

Where the blades of a front row are retracted to positions between theblades of a rear row there is introduced a variation in the ratio of thecross sectional areas at the throat and inlet of each passage, asremarked earlier. In some applications the variation in the throat areamay be less significant as for instance in operation at subsonic tipspeeds, or where low cost and simplicity are significant. Then a singlerow of blades may be employed which is movable axially from one localityto another of the main flow duct.

Thus in Figs. 1 and 2, for instance, only. the front blades 32 would bepresent. They would be retractable to a rear ward locality like thatoccupied by the rear'blades 33 as shown in these figures.

..Itwill. now be clcarwthat, I have. disclosed ,a, nov e1 compressorwhich can operate in the range of supersonic speed with the rate offluid flow increasing with increasing rate of rotation. Y

While I have illustrated specific forms of theinvcntion, it .is tobeunderstood 'thatvariations may be made therein and that Lintendto vclaim.my invention broadly as indicated by the appended claims. a

I claim:

1. In combinationrin a supersonic compressor for compressing/an elastic.fluid, :a case,. a. rotor. hub means positioned. inlsaidcase'forrotation aboutan .axis defining an annularductiwith.saidz'casetfor conduction of said-fluid, a first row of bladescarried on said hub means .at a forward locality thereof winperipherally spaced relation thereabout dividingsaidduct into aplurality of rotor flow passages, a second row ofperipherallyspacedblades carried on sai'd hub means rearwardadjacentto said first row,said hub means having decreasing diameters rearward cooperating withsaid case to provide increasing cross sectionalareas of said duct.rearward therealong, means to displace saidblades of-said first nowrearward to positions between said blades of said rear row where saidannular cross section at the inlet side of said blades is greater thanat said forward locality, and means to rotate said hub means and bladesat blade tip speeds relative to said fluid forward adjacent to saidblades greater than the speed of sound in said adjacent fluid.

2. In combination in a supersonic compressor for compressing an elasticfluid, a case, a rotor hub means positioned in said case for rotationabout an axis defining an annular duct with said case for conduction ofsaid fluid, a first row of blades carried on said hub means at a forwardlocality thereof in peripherally spaced relation thereabout dividingsaid duct into a plurality of rotor flow passages, 21 second row ofperipherally spaced blades carried on said hubmeans rearward adjacent tosaid first row, said hub means having decreasing diameters rearwardcooperating-with said case to provide increasing cross sectional areasof said duct rearward therealong, means to displace said blades of saidfirst row rearward to positions between said blades of said rear rowwhere the annular cross section at the inlet side of said blades isgreater than at said forward locality, each said blade having a sharpleading edge and increasing in thickness rearward therefrom, and meansto rotate said hub means and blades at blade tip speeds relative to saidfluid forward adjacent to said blades greater than the speed of sound insaid adjacent fluid.

3. In combination in a supersonic compressor for cornpressing an elasticfiuid, a case, a rotor hub means positioned in said case for rotationabout an axis defining an annular duct with said case for conduction ofsaid fluid, a first row of blades carried on said hub means inperipherally spaced relation thereabout dividing said duct into aplurality of rotor flow passages, 21 second row of peripherally spacedblades carried on said hub means at a forward locality thereof rearwardadjacent to said first row, said hub means having decreasing diametersrearward cooperating with said case to provide increasing crosssectional areas of said duct rearward therealong, means to displace saidblades of said first row rearward to positions between said blades ofsaid rear row where the annular cross section at the inlet side of saiddisplaced blades is greater than at said forward locality, each saidblade having a sharp leading edge and increasing in thickness rearwardtherefrom, said blades of said combined front and rear rows overlappingin axial view and having the leading edges of succeeding blades chord-Wise forward of the mid-chord points of preceding blades, and means torotate said hub means and blades at blade tip speeds relative to saidfluid forward adjacent to said blades greater than the speed of sound insaid adjacent fluid.

4. In combination ina supersonic compressorfor corn pressing an elasticfluid, a case, a rotor hub means positioned in said case for rotationabout an axis defining an annular duct with said case for conduction ofsaid fluid, a first row of blades carried on said hub means at a forwardlocality thereof in peripherally spaced relation thereabout dividingsaidduct into a plurality of rotor flow passages, a second row ofperipherally spaced blades carried on said hub means rearward adjacentto said first row, said hub means having decreasing diameters rearwardcooperating with said case toprovide increasing cross sectional areas ofsaid duct rearward therealong, means to rotate said hub means and bladesat blade tip speedsrelative to said fluid forward adjacent to saidblades greater than the speed of sound in said adjacent fluid, and meansto displace said blades of said first row rearward to positions betweensaid blades of said rear row as a function of .said .tip spcedswherebythe inlet side of said displaced blades isat a locality of greatercrosssectional area than at said forward locality.

5. In combination in a compressor for compressing an .elastic fluidaugenerally cylindrical case, a rotor hub means positioned in saidcase-for rotation about an axis defining an annularductwith said case,said duct being directed along said axis for conduction of said fluidtherethrough in the general axial direction, a row of blades in saidduct carried on said hub means at a forward locality thereof inperipherally spaced relation thereabout .with their leading edgesextending outward of said hub means in the general radial directions anddividing said duct into a plurality of rotor flow passages, said hubmeans having decreasing diameters rearward cooperating withsaid case toprovide increasing cross sectional areas of said duct axially .rearwardtherealong, and means to displace said blades rearward to a localitywhere the cross sectional area of said annular duct is greater than atsaid forward locality. I

6. In combination in a compressor for compressing an elastic fluid, agenerally cylindrical case, a rotor hub means positioned in said casefor rotation about an axis defining an annular duct with said case, saidduct being directed along said axis for conduction of said fluidtherethrough in the general axial direction, a row of blades in saidduct carried on said hub means at a forward locality thereof inperipherally spaced relation thereabout with their lea-ding edgesextending outward of said hub means in the general radial directions anddividing said duct into a plurality of rotor flow passages, said hubmeans having decreasing diameters rearward cooperating with said case toprovide increasing cross sectional areas of said ductaxially rearwardtherealong, said blades at the tips thereof fitting closely to the ductsurface of said case, and means to displace said blades axially rearwardto a locality where the cross sectional area of said annular duct isgreater than at said forward locality while retaining said blades insaid closely fitting relation to said duct surface.

7. In combination in a supersonic compressor for compressing an elasticfluid, a generally cylindrical case, a rotor hub means positioned insaid case for rotation about an axis defining an annular duct with saidcase, said duct being directed along said axis for conduction of saidfluid therethrough in the general axial direction, a row of bladeswithin said duct carried on said hub means in peripherally spacedrelation thereabout with their leading edges extending outward of saidhub means in the general radial directions and dividing said duct into aplurality of rotor flow passages, said duct having increasing crosssectional areas axially therealong, and means to move said bladesaxially in said duct to provide increased cross sectional areas for eachsaid rotor passage at the inlet thereof during rotation of said rotorhub means and said blades.

8. In combination. ina supersonic compressor for compressing an elasticfluid, a generally cylindrical case, a rotor hub means positioned insaid case for rotation about an axis defining an annular duct with saidcase, said duct being directed along said axis for conduction of saidfluid therethrough in the general axial direction, a row of bladeswithin said duct carried adjustably on said hub means in peripherallyspaced relation thereabout with their leading edges extending outward ofsaid hub means in the general radial directions and dividing said ductinto a plurality of rotor flow passages, said duct having increasingcross sectional areas axially therealong, and means to move said bladesaxially to provide increased cross sectional areas for each said rotorpassage at the inlet thereof during rotation of said rotor hub means andsaid blades as a function of the rate of rotation thereof.

9. In combination in a supersonic compressor for compressing an elasticfluid, a generally cylindrical case, a rotor hub means positioned insaid case for rotation about an axis defining an annular duct with saidcase, said duct being directed along said axis for conduction of saidfluid therethrough in the general axial direction, a row, of bladeswithin said duct on said hub means in peripherally spaced relationthereabout with their leading edges extending outward of said hub meansin the general radial direction and dividing said duct into a pluralityof rotor flow passages, and means to move said blades relative to saidhub means to provide increased cross sectional areas for each said rotorpassage at the inlet thereof during rotation of said hub means and saidblades.

10. In combination in a supersonic compressor for compressing an elasticfluid, a generally cylindrical case, a rotor hub means positioned insaid case for rotation about an axis defining an annular duct with saidcase, said duct being directed along said axis for conduction of saidfluid therethrongh in the general axial direction, a row of bladesWithin said duct on said hub means in peripherally spaced relationthereabout with their leading edges extending outward of said hub meansin the general radial direction and dividing said duct into a pluralityof rotor flow passages, and means to move said blades relative to saidhub means to provide increased cross sectional areas for each said rotorpassage with increasing rates of rotation of said hub means in responseto said increasing rates.

11. In combination in a supersonic compressor for compressing an elasticfluid, a generally cylindrical case, a rotor hub means positioned insaid case for rotation about an axis defining an annular duct with saidcase, said duct being directed along said axis for conduction of saidfluid therethrough in the general axial direction, a row of bladeswithin said duct on said hub means in peripherally spaced relationthereabout with their leading edges extending outward of said hub meansin the general radial direction and dividing said duct into a pluralityof rotor flow passages, said hub means having decreasing diametersaxially therealong cooperating with said case to provide increasingcross sectional areas of said duct axially therealong, and means to movesaid blades relative to said hub means to provide increased crosssectional areas for each said rotor passage at the inlet thereof duringrotation of said hub means and said blades.

References Cited in the file of this patent FOREIGN PATENTS 364,732Germany Dec. 1, 1922

